Intel 4040

The Intel 4040 ("forty-forty") is the second <a href="/facts/4-bit_computing/C0MF1C62">4-bit</a> microprocessor designed and manufactured by <a href="/facts/Intel/SMF0gJJX">Intel</a>. Introduced in 1974 as a successor to the <a href="/facts/Intel_4004/kAoetjSU">Intel 4004</a>, the 4040 was produced with a <a href="/facts/10_%25CE%25BCm_process/NNYHV09a">10 μm process</a> and includes <a href="/facts/Silicon_gate/rMkDbyqp">silicon gate</a> enhancement-load <a href="/facts/PMOS_logic/DWmuIrcn">PMOS logic</a> technology. The 4040 contained 3,000 <a href="/facts/Transistor_count/1oDVlhAY">transistors</a> and could execute approximately 62,000 <a href="/facts/Instructions_per_second/N23PAFGV">instructions per second</a>.
General performance, bus layout and <a href="/facts/Arithmetic_logic_unit/SgIjPzSc">arithmetic logic unit</a> (ALU) were identical to the 4004. The main improvement was to use a larger 24-pin <a href="/facts/Dual_in-line_package/Qgu6Jave">dual in-line package</a>, giving it 8 more pins than the 16-pin 4004. Two of these were used to implement <a href="/facts/Interrupt/Mm6C4rpc">interrupts</a>, which were lacking in the 4004 and considered a major oversight. Two more implemented a halt/stop system, which put the processor into a low-power mode and also allowed for single-step operation that made debugging much easier. Another pin was used to <a href="/facts/Bank_switching/9y09qE2k">bank select</a> a second <a href="/facts/Read-only_memory/P9QMuDLH">read-only memory</a> (ROM), doubling the amount of ROM the processor could address compared to the 4004.
To make use of these new pins, the <a href="/facts/Instruction_set/8p8vwUeE">instruction set</a> was expanded, increasing it to 60 instructions from the original 46. Additionally, the internal <a href="/facts/Register_file/NGvqUwe3">register file</a> and <a href="/facts/Call_stack/1sMt713v">pushdown stack</a> were expanded to support rapid interrupt processing.

Intel 4040 open-in-new

Intel 4040